[PATCH 6/6] habanalabs: fix mask to obtain page offset

[Oded Gabbay <ogabbay@kernel.org>]

From: Ohad Sharabi <osharabi@habana.ai>

When converting virtual address to physical we need to add correct
offset to the physical page.

For this we need to use mask that include ALL bits of page offset.

Signed-off-by: Ohad Sharabi <osharabi@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
---
 drivers/misc/habanalabs/common/mmu/mmu.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/habanalabs/common/mmu/mmu.c b/drivers/misc/habanalabs/common/mmu/mmu.c
index b37189956b14..792d25b79ea6 100644
--- a/drivers/misc/habanalabs/common/mmu/mmu.c
+++ b/drivers/misc/habanalabs/common/mmu/mmu.c
@@ -501,12 +501,20 @@ static void hl_mmu_pa_page_with_offset(struct hl_ctx *ctx, u64 virt_addr,
 
 	if ((hops->range_type == HL_VA_RANGE_TYPE_DRAM) &&
 			!is_power_of_2(prop->dram_page_size)) {
-		u32 bit;
+		unsigned long dram_page_size = prop->dram_page_size;
 		u64 page_offset_mask;
 		u64 phys_addr_mask;
+		u32 bit;
 
-		bit = __ffs64((u64)prop->dram_page_size);
-		page_offset_mask = ((1ull << bit) - 1);
+		/*
+		 * find last set bit in page_size to cover all bits of page
+		 * offset. note that 1 has to be added to bit index.
+		 * note that the internal ulong variable is used to avoid
+		 * alignment issue.
+		 */
+		bit = find_last_bit(&dram_page_size,
+					sizeof(dram_page_size) * BITS_PER_BYTE) + 1;
+		page_offset_mask = (BIT_ULL(bit) - 1);
 		phys_addr_mask = ~page_offset_mask;
 		*phys_addr = (tmp_phys_addr & phys_addr_mask) |
 				(virt_addr & page_offset_mask);
-- 
2.25.1